Atomised lidocaine for airway topical anaesthesia in the morbidly obese: 1% compared with 2%*

Abstract

SummaryAirway anaesthesia using atomised lidocaine for awake oral fibreoptic intubation in morbidly obese patients was evaluated using two doses of local anaesthetic. In this randomised, blinded prospective study, 40 ml of atomised 1% (n = 11) or 2% (n = 10) lidocaine was administered with high oxygen flow as carrier. Outcomes included time for intubation, patient tolerance to airway manipulation, haemodynamic parameters, the bronchoscopist's overall satisfaction, and serial serum lidocaine concentrations. Patients receiving lidocaine 1% had a longer mean (SD) time from the start of topicalisation to tracheal tube cuff inflation than those receiving lidocaine 2% (8.6 (0.9) min vs 6.9 (0.5) min, respectively; p < 0.05). Patients in the 1% cohort demonstrated increased responses to airway manipulation (p < 0.0001), reflecting lower bronchoscopist's satisfaction scores (p < 0.03). Haemodynamic responses to topicalisation and airway manipulation were similar in both groups. Peak plasma concentration was lower in the 1% group (mean (SD) 1.4 (0.3) and 3.8 (0.5) lg.ml )1 , respectively; p < 0.001). Airway anaesthesia using atomised lidocaine for awake oral fibreoptic intubation in the morbidly obese is efficacious, rapid and safe. Compared with lidocaine 1%, the 2% dose provides superior intubating conditions. Safe airway management in morbidly obese patients requiring general anaesthesia is of paramount importance and inadequate preparation may have dire consequences. At induction of anaesthesia, these patients can experience rapid arterial oxygen desaturation [1] and aspiration [2], and difficulties may be encountered at all levels of airway management including ventilation and intubation [3][4][5][6]. Securing the airway using awake fibreoptic intubation is considered to be a safe strategy [7], but this technique requires superior airway anaesthesia if excessive sedation is to be avoided. In the morbidly obese patient, obscured landmarks may limit the usefulness of invasive techniques (such as nerve blocks) to achieve airway anaesthesia [8]. Recently, we demonstrated that atomised lidocaine 2% or 4% is an efficacious, rapid and safe method to achieve topical airway anaesthesia in morbidly obese patients. However, the lowest optimum dose was not established [9]. This study was undertaken to compare atomised lidocaine 1% and 2% for airway anaesthesia during awake fibreoptic intubation in morbidly obese patients undergoing bariatric surgery. In a prospective, blinded and randomised investigation, main outcome measures included procedural time, patient tolerance to airway manipulation, haemodynamic parameters and serum lidocaine concentrations. The bronchoscopist's satisfaction level with intubating conditions and patients' tolerance to airway topicalisation were also assessed.

Local Airway Anesthesia Attenuates Hemodynamic Responses to Intubation and Extubation in Hypertensive Surgical Patients

“…Care should be taken when using these agents, however, because of delays in postoperative awakening and the occurrence of complications associated with a decline in cardiac function. Lidocaine as an airway topical anesthetic is widely used to attenuate hemodynamic reflexes [3,17,18,25,27–31]. Godzieba et al indicated that use high dose or high concentration of lidocaine (≤4 ampules) with epinephrine seems to be relatively safe for cardiovascularly compromised patients [51].…”

Practical aspects and training in fibreoptic intubation

“…The most appropriate concentration of atomised lignocaine is 2%, allowing better patient response and higher operator satisfaction compared to 1% lignocaine [28] and resulting in a smaller drug dosage and lower plasma concentrations compared with 4% [26]. Combining nebulization (lignocaine 4% 200 mg) and 'spray-as-yougo' (without sedation) produces good FOI conditions and patient comfort [24].…”

Lidocaine permeation from a lidocaine NaCMC/gel microgel formulation in microneedle-pierced skin: vertical (depth averaged) and horizontal permeation profiles

“…The smallest force of 3.9 N showed the lidocaine crossing over the toxic plasma level of lidocaine (5 µg/ml) at a time of nearly one hour. Usually a range of 5 to 10 µg/ml is considered to be a toxic concentration for lidocaine in blood plasma [55].…”